With the camera-embedded handset becoming very fashionable these days, the demand for a small picture taking lens that is thin and cheap grows tremendously. Besides the fixed focus lens module now widely used, the zoom lens module is a growing trend.
In the past, the zoom lens had to include at least six glass lenses to achieve two to three times of the zoom ratio. The total length of the lens is not suitable for thin portable devices.
In conventional techniques, U.S. Pat. No. 6,757,111 discloses a simple zoom lens with three times of zoom ratio. It contains six glass lenses. Three of them are Aspherical glass lenses. The length of the lens is about 9.4 times of the image height. It is too lengthy and expensive for camera handsets. U.S. publication No. 20040012859 has a lens with a length about 8.6 times of the image. It is also lengthy, and provides a lower zoom ratio (only two times). U.S. publication No. 20040136705 discloses a zoom lens of three zoom ratios, but the length of the zoom lens is about ten times of the image height. It is too lengthy to be used in a thin product.
Hence there is an urgent need to develop a small zoom lens with fewer glass lenses and more plastic elements to reduce production costs and meet market requirements.